In an automatic transmission for use in a vehicle, an operation of a select lever by a driver is detected by an inhibitor switch. The operating range of the automatic transmission is determined on the basis of a range signal (INH signal) from the inhibitor switch. Tokkai 2002-310292, published in Japan in 2002, discloses a control device which controls the engagement and disengagement of a forward clutch or reverse clutch (reverse brake) by means of hydraulic control. In such a control device, a manual valve is moved on the basis of a select lever operation performed by the driver, whereby oil pressure is supplied selectively to the forward clutch and reverse clutch. The position ranges of the manual valve include a drive range (D range) corresponding to the D range of the automatic transmission, a reverse range (R range) corresponding to the R range of the automatic transmission, and an N range corresponding to the N range of the automatic transmission. In the D range of the manual valve, oil pressure is supplied only to the forward clutch. In the R range of the manual valve, oil pressure is supplied only to the reverse clutch. In the N range of the manual valve, no oil pressure is supplied to either the forward clutch or the reverse clutch.